Digital light processing (DLP) projection apparatus includes an illumination system, a digital micro-mirror device (DMD) and a projection lens. The illumination system is used to provide an illumination beam; the digital micro-mirror device is used to convert the illumination beam into an image beam; and the projection lens is used to project the image beam onto a screen, thereby forming images on the screen. Conventionally, illumination system usually uses high pressure mercury lamp as light source for providing white lights as the illumination beam. However, with the development of illumination technology, light emitting diode (LED) and laser light source with power saving feature have gradually been used as the light source for the illumination system.
FIG. 1 is a schematic view of a conventional illumination system provided with a laser light source. In the conventional illumination system 100 as shown in FIG. 1, a blue beam 112 provided by a laser light source module 110 sequentially passes through a collimator element 122, a dichroic mirror 130 and lenses 123, 124 and then emits onto a rotating phosphor wheel 140. The phosphor wheel 140 may include a green phosphor area, a yellow phosphor area and an opening area. A back 141 of the green phosphor area and the yellow phosphor area of the phosphor wheel 140 is correspondingly disposed with reflective elements (not shown). The blue beam 112 sequentially emits to the green phosphor area, the yellow phosphor area and the opening area. A green beam 113 and a yellow beam 114 are generated when the green phosphor area and the yellow phosphor area are emitted and excited by the blue beam 112, respectively. The green beam 113 and the yellow beam 114 are reflected to the dichroic mirror 130 by the reflective elements. Then, the green beam 113 and the yellow beam 114 are reflected by the dichroic mirror 130, and the green beam 113 and the yellow beam 114 pass through a lens 125 and then sequentially emit onto a rotating wheel 150. In addition, a portion of the blue beam 112 sequentially passes through the opening area, lenses 126, 127, reflective elements 161, 162, a lens 128, a reflective element 163, a lens 129, the dichroic mirror 130, the lens 125 and then emits on the color wheel 150.
The color wheel 150 has a red filter area and a transparent area corresponding to the aforementioned yellow phosphor area, a green filter area corresponding to the aforementioned green phosphor area, and a diffusion area corresponding to the aforementioned opening area. Through controlling the color wheel 150 and the phosphor wheel 140 to rotate with each other, the green beam 113 emits to the green filter area, the yellow beam 114 emits to the red filter area and the transparent area, and the blue beam 112 emits to the diffusion area (not shown). Thus, the beam passing through the color wheel 150 and then entering a light integration rod 170 contains blue, green and red beams for forming color images and yellow beams for enhancing the brightness.
However, as shown in FIG. 1, the conventional illumination system 100 has a relatively complicated structure and requires a lot of optical components; therefore, the conventional illumination system 100 has some disadvantages such as higher cost, larger component size and poor optical efficiency.
The information disclosed in this “BACKGROUND OF THE INVENTION” section is only for enhancement understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Furthermore, the information disclosed in this “BACKGROUND OF THE INVENTION” section does not mean that one or more problems to be solved by one or more embodiments of the invention were acknowledged by a person of ordinary skill in the art.